1. Field
The present application generally relates to animation technology, and, more particularly, to placing skin-attached features on a computer-generated character.
2. Related Art
Media productions have employed increasingly complex animations in order to construct increasingly realistic images. In addition to animating surfaces, increasing attention has been directed towards surface-attached features including hairs, fur, scales, and feathers. See, U.S. Patent Publication No. 2003/0179203; U.S. Pat. Nos. 6,720,962; 6,952,218; and Kim, T.-Y., and Newmann, U., Interactive Multiresolution Hair Modeling and Editing, ACM Transactions on Graphics 21, 3, pp 620-629 (July 2002).
Feathers, in particular, have been a challenging feature since the early days of animation. Birds of early animation films were often secondary characters with relatively few unrealistic feathers. Although more realistic effects have been achieved in modern animation, challenges remain especially for animating birds with a large number of feathers throughout an animation sequence. The visual complexity in producing believable bird characters requires realization of their numerous feathers in relation to a skin surface. The approximation of such skin covered with attached features as feathers, scales, hair, and fur adds considerable challenges beyond typical character animation.
Depending on the degree of modeling complexity, there may be numerous feather-describing attributes that can be represented by either a small set of numbers (e.g., length and width) or with more detailed parametric shape information. Numerous papers have proposed various parametric models of feathers. See, Franco, C. G., and Walter, M., Modeling the Structure of Feathers, sibgrapi 00, p. 381 (2001); Chen, Y., Xu, Y., Guo, B., and Shum, H.-Y., Modeling and Rendering of Realistic Feathers, ACM Transactions on Graphics 21, 3, pp. 630-636 (July 2002); and Streit, L., and Heidrich, W., A biologically parameterized feather model, Computer Graphics Forum 21, 3, pp. 565-574 (2002). The animation of these attached features in conjunction with the corresponding skin surface presents substantial challenges for existing animation technology.
Thus, there is a need for improved animation for characters with surface-attached features, such as hairs, fur, scales, and feathers.